Dispelling nutrition myths, ranting, and occasionally, raving

Bacteria: the next weight loss craze?

Recent research has indicated that a change in gut microbial flora following gastric surgery may contribute to weight loss in patients. This conclusion was reached following a study on mice. A group of mice underwent gastric-bypass surgery, their gut microbial flora was monitored, and then some of that bacteria was transferred into mice that had not undergone surgery.

There were also two other groups of mice that underwent “sham” surgeries (their intestines were snipped apart and then reconnected). One of these groups continued to be fed a high calorie diet post-surgery while the other was put on a restricted diet.

There are a few things about this study that intrigue me. I think it’s important to note that the mice place on the restricted diet lost the same amount of weight as the mice that underwent the true bypass surgery. To me, this indicates that the level of obesity in these mice may not have been the same as the level required for weight loss surgery in humans.

I also find it curious that the mice that received the gut flora apparently had no pre-existing gut flora of their own. I’m not sure if this is an error in reporting but you would be extremely hard-pressed to find a human without pre-existing gut-flora (perhaps if they’d been on a very high dose course of antibiotics). We also know that gastric bypass surgery can result in nutrient deficiencies and it’s possible that the presence of the bacteria found in these post-surgical mice might also increase the risk of malnourishment.

Finally, and most importantly, even if weight loss in mice can be attributed to the presence of certain bacteria in the gut, mice are not the same as humans. Do mice have the same gastro-intestinal flora as humans? Do they react to surgery in the same way as we do? Do they have the same relationship to food as we do? I would hazard to guess that the answer to all of these questions is no.

While this research is very interesting, and may in the long-term provide us with further insight into obesity and weight management, at this point I would be extremely cautious when interpreting the results.